It is well known to use an electronic engine control to control various aspects of an internal combustion engine. As one example, engine controls are often used to control the ignition circuit which fires an ignition element corresponding to each cylinder of the engine. In such an arrangement, the engine control may be used to adjust the timing of the firing of the ignition element and thus advance or retard the ignition based on an operating condition of the engine.
Along these same lines, the engine control may be used to entirely prevent the firing of the ignition element of one or more cylinders or to so substantially adjust the timing of the firing to misfire one or more cylinders under certain operating conditions. This prevention of firing or substantial misfiring is generally referred to as cylinder disabling, since combustion does not occur in the cylinder at all or occurs at a time which is ineffective in powering the engine.
It has been proposed to use the cylinder disabling feature when the engine is idling. When the engine is idling, the firing of some but not all of the cylinders has the advantage that engine temperature is reduced since combustion is not occurring in one or more of the cylinders. When fuel is not supplied to the disabled cylinder(s), the fuel consumption rate of the engine is also advantageously decreased.
A significant disadvantage to such a cylinder disabling strategy is that the operator of the engine has no control over whether the control unit operates the engine in a disabling mode. In general, the control is arranged to operate the disabling mode anytime an indicator of engine idling is provided. In some instances, however, this indication may be provided when in fact the operator of the engine desires a high engine power output.
It is an object of the present invention to provide an engine control which employs a cylinder disabling mode at certain engine idle conditions, but which is arranged to prevent operation of the cylinder disabling mode during certain other conditions.